Oil and gas heat exchanger cleaning

Partly. Where a train has spare exchangers or can be run with one bay bypassed, in-situ chemical or solvent circulation on the isolated unit can recover some preheat without taking the whole unit down. It is a holding measure and it is aimed at reaching the planned turnaround instead of replacing it.

It cannot address the shell side with the bundle in place, and it does nothing for coke. Anything that has thermally cracked onto the tube wall needs the bundle out and a lance on it.

Decontamination is chemical treatment applied before the unit is opened, to remove hydrocarbon, drive off H2S and benzene to safe entry levels, and oxidise pyrophoric iron sulphide. It is usually circulated or applied in the vapour phase during the shutdown sequence.

Not every exchanger needs it. Clean utility service does not. Anything on sour, benzene-bearing or heavy hydrocarbon service generally does, and deciding is early because it sits on the critical path ahead of every cleaning activity.

By never letting it dry in air. Iron sulphide formed in sour service oxidises exothermically once it dries, and it has ignited hydrocarbon vapour in opened equipment often enough that it is treated as a standing hazard, not an unusual one.

In practice that means the unit is kept wet from the moment it is opened, or the sulphide is chemically oxidised during decontamination so there is nothing left to react. Deposits removed during cleaning are kept wet in the skip too and not left in the sun.

The cleaning itself is often the shortest part. A bundle in a cleaning bay with lances running is typically a matter of hours to a day depending on tube count, bore and how hard the deposit is.

What sets the elapsed time is everything around it: isolation, decontamination, breaking the joints, the pull, transport to the bay, the queue at the bay, inspection, the rebuild and the test. On a turnaround with many bundles the bay capacity, not the lance, is usually the constraint.

Jetting water that has been in contact with hydrocarbon is a controlled waste and it does not go to drain. Work is done in a bunded bay or with a containment mat, and the water is collected, separated and either recycled through the jetting spread or removed under duty of care.

Solids are handled separately. Coke, sludge and sulphide scale are drummed or skipped wet, characterised and disposed of accordingly. Where a site has its own slops route, cleaning is planned around it.

Yes. A bundle that has been pulled is inspected before rebuild: visual and, where specified, eddy current or IRIS to find wall loss the cleaning has exposed, and the exchanger is pressure tested once reassembled.

Cleaning frequently reveals damage instead of causing it. Deposit sitting on a thinned tube can be the only thing holding pressure, and finding that on test is considerably better than finding it on start-up.

Bundle count, deposit and access, in that order. A soft-fouled bundle with a straightforward pull is not comparable to a coked hot-end exchanger needing decontamination, drilling and full inspection.

The costs that surprise people are rarely the cleaning. Decontamination, containment, waste disposal and crane time frequently exceed the jetting itself, so the enquiry asks for the deposit and the unit instead of a bundle count alone.

Fouling here is monitored, not scheduled. The usual practice is to trend measured heat transfer against clean-condition performance and watch the gap open, which gives a real fouling curve for that service on that crude slate.

Turnaround interval then decides what is possible. The useful question is normally not how often, but which exchangers earn their place in the next window, and that is a ranking exercise off the fouling curves rather than a calendar.